The present invention relates generally to audio visual teaching devices and more particularly to an improved teaching device of the type shown and described in U.S. Pat. No. 3,869,718 to Josef Schmidt, filed June 6, 1973 and assigned to the assignee of the present invention, which application disclosure is incorporated by reference in this application but includes the instantaneous feedback system herein described.
Teaching machines employing a drive system for moving an information card including a magnetic stripe through a guide channel past a transducing head are well known in the art. Generally, such machines transport the card past a transducing/recording head which reads a sound track containing a magnetic recording of selected "model" audio information. The simultaneous stimulation of different physical senses has been recognized by educators as an efficient method for the teaching of foreign languages, for example. Therefore, corresponding information in the form of a picture or the like usually is printed on the card to stimulate the student visually at substantially the same time as the student is being stimulated audibly.
Prior art machines also have permitted the student to record his own voice on a second track of the magnetic stripe so that he may replay his pronunciation and compare it to the model. As noted above, this type of teaching machine is particularly applicable to the teaching of a foreign language where continued practice is needed for the correct pronunciation of a foreign vocabulary. The teaching of known words or phrases to young or retarded students also is an important use of such machines. Also, since many students usually are in one room or "learning laboratory", it is necessary and desirable to use headphones in order to permit simultaneous operation of several teaching machines by a large number of students.
It is known that, when speaking normally, one hears his own voice in a different manner than one hears other people in normal conversation. This is due to the fact that one hears his own voice simultaneously by two acoustic channels. One channel is an external, aerial route between the mouth and ears. The second channel is by internal, bone conduction, between the vocal and auditive organs. This phenomenon is confirmed in every day life by the well known fact that any one who hears his own voice from a tape recording finds it unrecognizable in comparison with the sounds he is accustomed to hearing when listening to himself speak normally. This distortion of tonality is a major cause of difficulties experienced in acquiring good pronunication of a foreign vocabulary, for instance. Particularly, when a set of headphones is being used by the student during a particular learning session, the sound vibrations which travel through the air are substantially muffled by the headset and therefore the student can hear the word he is pronouncing only through the second or bone conduction route. Therefore the word appears to be very distorted since we are accustomed to hearing what we are saying through both acoustic channels.